Amplitorque controllable pitch propeller



April 10, 1951 H. .1. NICHOLS AMPLITORQUE CONTROLLABLE PITCH PROPELLER 2 Sheets-Sheet 1 Filed Aug. 20, 1945 weer J Maw/04s g fi V 74% Q April 10, 1951 AMPLITORQUE CONTROLLABLE PITCH PROPELLER Filed Aug. 20, 1945 H. J. NICHOLS 2,548,045

2 Sheets-Sheet 2 Patented Apr. 10, 1951 AMPLITORQUE CON TROLLABLE PITCH PROPELLER Harry J. Nichols, New York, N. Y.

Application August 20, 1945, Serial No. 611,481

Claims.

This invention relates to controllable and re-' versible pitch propellers, and particularly to propellers for marine use and for hydraulic prime movers, and has for one of its principal objects the provision of a propeller of the character described in which the pitch of the blades can be quickly and accurately regulated while the propeller is in rotation under load and in which the blades will be automatically locked against displacement from the pitch to which they have been set during such regulation.

Another object is to provide an exceptionally simple, compact, and powerful variable pitch propeller hub and blade actuating mechanism which is economical to manufacture, easy to install and service, and which will ensure reliable operation for long periods without special attention or maintenance.

A further object is to provide a controllable propeller which may be readily applied to existing propulsive installations with the minimum of modification of existing components and arrangements, thus securing substantial economies in modernizing installations already in service by the application of controllable pitch propellers thereto. A further object is to provide a strong and rigid pitch varying mechanism which eliminates any possibility of flutter or vibration of the blades in operation due to excessive elasticity or backlash in the pitch varying mechanism.

A further object is to provide a pitch varying system of adequate angular range, including reversing of the blades, which is capable of changing the blade pitch in micrometric increments, yet also is capable of changing the pitch at a rapid rate for maneuvering and meeting emergencies.

A further object is to provide a pitch regulating system whose operating speed is independent of the speed of rotation of the propeller shaft.

A further object is to provide a construction in which the gears of the primary actuating mechanism are relieved of any strain excepting when the pitch is being varied, thereby reducing the wear on the gear teeth and enablingrelatively light gearing to be employed.

A further object is to provide blade actuating mechanism operatively mounted in the hub so that the great stresses due to the powerful hydrodynamic twisting torque on the blades under load are confined to the hub and a rigid and strong blade actuating mechanism of minimum size and cost is obtained.

With these and other objects in view, as well as other advantages incident to the improved construction, the invention consists in thevarious parts and combinations thereof set forth and claimed, with the understanding that the several necessary elements constituting the same may be varied'in proportions and arrangement without departing from the nature and scope of the invention as defined in the appended claims.

To enable others skilled in the art to comprehend the several underlying features of this invention, that they may embody the same by suitable modifications in structure and relation to meet the various practical applications contemplated by the invention, drawings showing a preferred embodiment of the invention form part of this disclosure, and in such drawings like characters of reference denote corresponding parts in the several views in which Fig. 1 is a side elevation in partial axial sec- .tion of the unitary flange coupling and driving motor forming part of the invention.

Fig. 2 is a transverse sectional view taken sub'- stantially on line 2-2 of Fig. 1.

Fig. 3 is a side elevation in axial section of the hub of a variable pitch propeller and drive shaft therefor embodying certain features of the invention.

Fig. 4 is a transverse cross section of the propeller of Fig. 3 taken substantially on line 44 of Fig. 3.

Fig. 5 is a top View of the hub of Fig. 3 shown with the blade and blade mounting dismantled so as to disclose the construction of the slide portion of the cross-head and other details.

Fig. 6 is a transverse cross section of the gear mechanism taken on lines 6-6 of Fig. 3.

Referring now to the drawings and particularly to Figs 1 and 2, a preferred construction of a controllable pitch propeller system embodying the invention is shown as comprising a hollow main shaft It), as for example the shaft of a prime mover, having a collar or annular flange I I upset or otherwise provided thereon at one end, and a propeller shaft 30 having mounted thereon a demountable flange 3|, the two being connected in driving relation by means of a novel unitary flange coupling 20 in which is housed a pitch changing motor and other mechanism to be described in detail hereinafter.

The actuating motor is preferably a polyphase induction motor having a squirrel cage rotor 15 mounted on a shaft l4 journalled in bearings suitably mounted in end shields I6, I! in concentric relation to the bore of a laminated stator it having typical distributed windings I9. The end shields and stator are suitably assembled to tubular shell or frame 2| as shown or in any preferred manner, thereby to provide a complete motor unit. v 7

A hollow cylinder or barrel 22 comprises the main structural componentof thespecial flange coupling. Suitably mounted on barrel 22 but insulated therefrom by an insulating band 23am two series of slip rings designated by 24 and 25 respectively, and riding thereon are brushes 2%; and 2?, shown schematically since the construction of slip ring and brush assemblies arewell known. Insulated conductors 2B provideapath for current from slip rings 24 to winding [9,

while insulated conductors 29 provide electrical connections from slip rings ze to electrical trans,- mitter l3 mounted on end shield I6 and forming part of an electrical pitch indicator system, but.

by screws to barrel 22 and the motor is mounted on plate 34 by screws tapped into end shield ll, or otherwise as desired, thereby providing a unitary assembly for theentireflange coupling, including the motor and electrical transmitter. The flange coupling 201s assembledto the shaft flanges by cap screws 32 passing through suitable longitudinal holes in flangetl, split shaftlocking ring 33- andfiangefplate 3t, and screwed into threaded holes in barrel 22;.whilecap screws i2 pass through longitudinal holesin flange it and are screwed into threaded holes. in barrel whereby when these cap, screws are. tightened these parts are tightlyclampe'd together in rigid driving relation; Demountable flange 3,5 is keyed to-propeller shaft 39 by multiple keys 38,- one key being shown.

Motor shaft l i is provided at one end with an extended output shaft ii), extending into elec-, trioal transmitter l3 for driving same, and atthe other end with a second splined output shaft M. An internally splined sleeve 52. couples output shaft M to the splined end it of torque shaft 15, the latter being mounted rotatably and concentrically in the bore of tubular propeller shaft 36 by a series of sleeve bearings lll assembled tightly on torque shaft 45, oneof the bearings M being shown, while other bearings are mounted at several points along the shaft inwell known manner.

Flange plate 34 is provided with. a peripheral lip 35 and barrel 22 with a projectingv shouldertfi, the space between the lip and the shoulder providing a groove in which is assembled an annular oil sealing ring of special construction to enable lubricating oilto be supplied to the rotating shaft assembly. The lubricating oil is maintained at a certain hydrostatic pressure and fills all thevoid spaces in the flange coupling, motor, propeller shaft and hub, thus providing continuous oil lubrication to all the working and bearing surfaces.

The oil sealing ring 50comprises a metallic bellows of thinnon-corrodable metal, such as stainless steel, the lips of which exert a light spring pressure on the adjacent side walls of the groove. This spring pressure is augmented by the oil pressure, which as stated is maintained at a level somewhat greater than the hydrostatic pressure on the propeller hub. It is intended that a slight leakage of oil shall occur at the joint between the bellows lips and the walls of the groove, thereby providing continuous oil lubrication of the sliding metallic surfaces. Two split rings 5 5, preferably of vulcanized fibre or the like, are assembled in the inner folds of the bellows and; are loosely fitted to the shaft, these split rings'serving to prevent the lips of the bellows from riding on the bottom of the groove, thus avoiding wear at the edges of the bellows lips. A circular tube 52 ismounted in the middle fold of the bellows as shown, being secured thereto by soldering or otherwise as desired. A series of radial holes 53 extend through the inner walls of the tube 52 and the middle fold of the; bellows, to enable oil flowing in tube 52 to enter the sealed space in the bellows, and via radial holes 545 in barrel 22 to reach the interior of the coupling, The bellows and the ends of tube 52 are brazed into a fitting 55, provided with a threaded stem, 55 adapted to mate with hollow nut 51-, andin combination therewith to provide a tight con.- nection with oil supply tube 58, all in well known manner.

It will be observed that the construction of the novel unitary flange coupling described obviously permits of ready and accurate assembly of the various parts, and of ready disassembly to replace the oil sealing ring 50, should this becomenecessary, the oil sealing ring being theonly Dart which is normally in rotation relativetoithe shaft and therefore being most subject: to wear.

Referring now to Figs. 3 to, 5;:inclusive, and particularly to Fig. 3-, whichshow one form ofpropeller hub construction according to theinvention adapted for use with the motor drive of the unitary flange coupling previously; described, the propeller hub Eli, is fixed tightly to the flange 3,9 of thetubular propeller-shaftBfl-by a series, of circularly arranged cap screws 6! -(one being shown) or otherwise as desii'ed. A- hub cap 8fl isjsecured tohub (Bil-by aaplurality ofilongitudinally disposed capscrews Si, or otherwise as desired. The hub 66.115 formedwithaplurality of radially extending circular sockets 32, and has longitudinal ribs 63 diametrally crossing-thereunder, each rib having formed. integral therewith a, center pin 64 with its radial axisconcentric with the bore of the associated socket. Each socket 62 is. step bored to receive a closely fitting-bearing-ring. 65

adaptedto besecured therein: by multiple cap screws 66 as shown. Blades 10, each havingga rootportion or boss ii to which a crank pin ring 12 having an integral crank pin-l3 canine attached by multiple cap screws-M; are rotatably mounted in the sockets $2 in the following manner: Each crank pin. ring "52.15 provided with a concentric bore lined with a.bearing;-l5,- rotatably fitted to center pin 5 and ,with-a step shoulder 69-.; (The cross-head lEltl is assumed-to be in place as shown in Fig. 3, and theslipper blocks lilt to beinthe position shown in Fig. 5.) The crank pin 13 is entered into the bore of the slipper blockand ring 72 lowered into socket 52. After the ring," is in place, bearing ringBE-isassembled in :the. socket and cap screws 66 screwed tightly in place. A fiat, thin cover ring 8'? is placed in the socket to cover-the heads ofcap screws 66 and a non-. ferrous sealing ring 68, haying-an archedsection-v to provide a limited amount of resiliency when subjected to pressure, is placed in the socket over the cover ring. The blade root II is then centered on the center pin 64 and cap screws 14 inserted in the threaded holes in the crank pin ring 72 and screwed up tight, thereby placing the sealing ring 68 under a predetermined pressure insufficient to squeeze out the oil film between the sealing ring and the blade root, but suflicient to prevent any material leakage of oil.

The construction described enables the blade to be rotated readily and accurately while providing adequate bearing area to accommodate the powerful forces on the blade while in rotation under load, and also provides a durable seal to prevent excessive leakage of lubricating oil at the blade sealing joint, yet permits a slow seepage of oil outwardly to prevent the entrance of Water into the hub. The blade mounting and sealing arrangement described is known to give reliable operation during years of operation.

Referring again to Figs. 3 to 6 inclusive, one form of novel blade actuating mechanism according to the invention comprise generally a power screw jack mounted axially in the hub 60 and operatively connected to turn the blades, and differential gearing mounted at the end of the hub opposite to the propeller shaft, which gearing receives torque from torque shaft 45 and supplies greatly amplified torque to the screw member 90 of the power screw jack.

Torque rod 45 extends coaxially through hollow power screw 90 and is mounted rotatably in bearing 82 carried by an integral strut 83 of hub cap 80 and in bearing 84 carried in the bore of power screw 90.

Mounted tight on rod 45, preferably by a tight splined connection as shown, is a planetary carrier assembly comprising two discs 85, 86 assembled together by cap screws 81 and stud sleeves 88. (See Fig. 6.) These discs carry two tight short axles 89, on which are rotatably mounted two planetary pinions PI and P2, which pinions have the same number of teeth, but the teeth on the two halves of pinion P2 are staggered in order to mesh properly with the two internal gears GI and G2 of the differential gear train. Internal gear GI is rigidly fixed to hub 60 by a plurality of cap screws 9I as shown or as may be desired.

Internal gear G2, which is the driven gear in the gear train, is a component part of the power screw, and may have internal teeth out on the inner periphery of flange 92 as shown or may be an assembled component. To provide differential action, gears GI and G2 vary by one tooth; for example GI may have 55 teeth, while G2 may have 56 teeth. As is well understood in the gear cutting art, the pitch circles to which the gear teeth are out are suitably adjusted to provide smooth meshing of the pinions with the gears, even though the gears have a different number of teeth.

Power screw 93 is journalled in a bearing 93 in the shaft end of the hub and in a cylindrical bore 94 at the opposite end of the hub. A thrust plate 95 is set in the bore 94 of the hub to provide one thrust bearing surface for flange 92, and a bearing ring 56 is assembled between flange 92 and the rim of GI to provide a second thrust bearing surface. In this manner, the thrust on power screw 90 due to the blade reaction is taken up in structural parts within the hub by adequate thrust bearing surfaces.

A triangular cross-head I00 is mounted as a nut on power screw 90 in such manner that the rotation of the power screw will translate the cross-head axially in the hub. In order to permit of assembly to the cross-head in the one piece hub (which is the generally preferred and simplest construction), the slide portions IUI of the arms of the cross-head are made separate; being assembled after the cross-head is in place by cap screws 71, access for that purpose being obtained through the blade sockets before the blades are assembled as shown in Fig. 5. Slipper blocks I03, each having a bore to receive one of the crank pins I3 of crank pin rings 72, are closely fit in the transverse slide portions of the cross-head. Further, the cross-head is provided with a longitudinal key 18 which slides in a key way in one of the ribs 63 to resist the tendency of the cross-head to rotate when the power screw is rotated under load. The cross-head is also preferably formed with central bosses which serve as stops against the hub 60 or plate 95 at the end of the stroke of the cross-head in event the normal working stroke is exceeded and thus function as pitch limit stops without damage to the operating mechanism.

The operation of the construction described is as follows: When the pitch is to be varied, the actuating motor is electrically energized to produce rotation of rotor I5 in one rotary direction or the other, thereby rotating torque shaft 45 in the same direction. Planetary carrier is rotated accordingly and pinions PI and P2 revolve in planetary motion in mesh with stationary gear GI and driven gear G2. At the end of one revolution of the planetary carrier these pinions by planetary action have meshed with all the teeth of gear GI (assumed to have 55 teeth) and with an equal number of teeth of gear G2 (assumed to have 56 teeth). Thus gear G2 is caused to advance (or lag) gear GI by one tooth pitch, producing a corresponding differential rotation of the two gears. Since internal gears of the type described are known to be highly eflicient, the torque amplification factor in the gear stage described is substantially equal to the speed reduction ratio. In the example chosen, since the speed reduction ratio is 56 to 1, the torque amplification factor would be approximately 55X.

Since gear GI is fixed to the hub, rotation of gear G2 relative to gear GI produces rotation of power screw in the threaded bore of crosshead I00 thereby causing axial translation of the cross-head in the hub and consequent rotation of the blades in their sockets.

Referring now to Figs. 3 to 5, it will be noted that the arms IDI of cross-head I D0 are fitted with transverse slide channels I02 adapted to receiver slipper blocks I03 each having a bore I04 fitting a crank pin I3 of one of the crank pin rings 65, each of which is attached to the root portion of one of the blades I0. As may be best seen in the upper part of Fig. 5, when crosshead I00 moves in an axial direction, each of the crank pins 13 will be forced to rotate in unison, the slipper blocks I03 sliding in the slide channels I02 as indicated to accommodate the transverse component of the crank pin motion. It is to be noted that the construction described enables a rigid and closely fitted operative connection to be employed between the power screw and the blades, thereby avoiding any degree of back-lash or elasticity likely to permit of vibration of the blades when under load. It is also to be noted that the power screw-jack can readily be made self-locking; i. e. the blade reaction 7 rendered incapable org-causing. rotation of the power screw, and this is the'pi'eferredconstruction. Furthermore, the difie r'ential gearing def scribed is inherently self-locking, since gears GI and G2 are positively lockedagainst relative rotation by pinions PI- and P2, except when these pinions are driven in planetary revolution. The blade actuating system describe'dis there foreinherently self-locking in any positionto which it is set; that is, the system cannot be actuated in reverse by the reaction of the blades.

The operation of the entire blade; actuating system of the invention is as fol-lows: Normally, when the propeller shaft is in rotation, all the parts rotate bodily'with the shaft and are at rest relativeto each other, except that the brushes 2'6 and 2! are stationary and ride on the rotating slip rings Zdan'd 2 To vary the pitch, the motor is supplied with current from a reversing controllennot shown, via brushes 26, slip rings 24- and-the internal conductor-s 2 8 to energize windings l9 and thereby produce rotation of the rotor l5- inone direction or theother. Torqueshaft 45 is driven by rotor through coupling sleeve l2- to rotate planetary carrier 85, thereby causing planetary revolutions of the pinions PI and P2 in internal gears G3 and G2,

The differential gear action previously described causes gear G2- to progress at reduced speed and amplified torque relative to gear Gl, thereby forcing rotation of power screw 9 3 in the threads of cross-head I96} and axial translation of the cross-head. The motion of the cross-head is transmited' by slipper blocks} tilt to the crank pins 13, forcing rotation of the blades. When rotation of the blade ceases, the

blades remain set at thatpitch until subsequent variation of the pitch by actuating operation as described. It is of course obvious thatthe rate of pitch adjustment is} entirely independentof the shaft speed, and therefore can be accor plished with equal facility with the pro eller shaft at rest or" in rotation at" any s'p'e'ed. This is animportant feature in providing rename and rapid pitch regulation under all operatingconditions.

It is further to be noted that because of the two-stage speed'reduc'tiorr and torque amplification provided, the speed reduction ratio may readily be as much as 3000:1 or evengreater, and the torque amplification factor 2000 or more times" the motor torque. Hence a small, high speed ac} tuating motor can be employed to advantage, and the pitch of the blade can be varied slowly in micrometric increments orrapidly" over the range from full forward to full r'ev-e'rseby' con of the blade setting, by eliminating external me-e chanical drive, andby inherent simplicity, econ-=5 omy; reliability andother features, the con:

trollable': pitch propeller system of the invention overcomes the disadvantageswhich have limited the application of; mechanicalvariablepitchpro-j pellers of the prior art.

'1. in combination with a variable pitchpro-- pell'r having a hollow propeller shaft, a hollow huliiixe'd thereon, and a plurality of axially rotatable'b'lades mounted on said hub, of mechanism operatively mounted substantially within hub forrotating' said blades axially in unison td'vary their pitch comprising, a power screwjack including a hollow rotary driving screw and translatory non-rotatable driven nut-member mounted coaxially with respect to each other and said hub, means adapted toconvert translatory motion of said driven member to axial rotary motion of said blades for operatively connecting said nut-member to rotate said blades ax lly in unison, torque amplifying differential ig' mounted coaxially in said hub and opively connected to rotate the driving screw of said power jack, and means including a torque shaft pa'ss'ingcoaxially through said driving screw for applying driving torque to said dilferential gearing.

2. A variable pitch marine propeller having, in combination, a hollow hub, a plurality of axially rotatable blades mounted on said hub, and mechanismo'peratively mounted within said hub for rotating said blades axially in unison under load comprising, a screw-jack including a hollow rotary' driving screw and a translatory driven nut mounted coaxially in said hub, means adapted to convert translatory motion of said nut toaxial rotary motion of said blades for operatively connecting said driven nut to said blades in common, differential gear means adapted to increase greatly the driving torque operatively connected to said driving screw, and power means includa torque transmission shaft passing coaxially "gh said driving screw for applying reversible driving torque to said gear means.

3. Ina variable pitch marine propeller, in combination, a hollow hub, a plurality of blades mounted fo'r axial rotation on said hub to vary I claim:

their pitch, and mechanism mounted withinsaidhub for applyinggreatly amplified driving torque to; rotate said:blades axially in unison while under lo'ad'co npri sing, a screw-jack including a' ho'll o'w rotary jack-screw mounted coaxially with respect to said; hub and a translatory driven nutme'mbe'r mounted non-rotatably on said jack-screw,- means for converting translatory motion of' said nut-member to axial rotary mo:

tion of said blades operatively connecting said nut-member to said blades, differential gear means characterized by a large torque gain ratio operatively connected to rotate said jack-screw; and povver means including a torque shaft passiiig 'coaxially through said jack-screw for applying reversible driving torque to said differential gea'r'm'eans. v

4}. In a're'vei sible variable pitch marine propeller, in combination with a hollow main hub structure having a plurality of blades mounted for axia'l rotationthe'reo'n to vary their itch, of mechanism operatively mounted substantially within said hub structure for rotating said blades axiallyin'unison While under load comprising, a

scr'evvjack having a rotary driving screw and a translatory driven nut' member mounted centrally with respect to said hub, a mechanical movement operatively connecting said member tosaid-bladesso as to rotate them axially bya translatory movement of said member, and power means including a torque transmission shaft passing coaxiallythrough said'screw-jack'mechanism andwdiiferential gearing characterized by. a large torque multiplying ratio operatively connected to be driven by said shaft for applying greatly amplified driving torque to said rotary driving screw.

5. A controllable and reversible pitch propeller system including a tubular propeller shaft and having, in combination, a liquid-tight hollow hub structure fixed coaxially on said shaft comprising a one-piece hub having radial sockets fixed tightly to said shaft and a liquid-tight cap secured tightly thereto, a plurality of axially rotatable blades having journals secured rotatably but tightly in the sockets of said hub; and mechanism operatively mounted within said hub for applying greatly amplified torque so as to rotate said blades axially in unison for the purpose of varying and reversing the pitch of said blades while under load comprising, a power screw-jack mounted coaxially in said hub between said journals, means for converting translatory motion to rotary motion operatively connecting said screw-jack to said blades, diiferential gearing mounted coaxially in said hub in driving relation to said screw-jack, and power transmission means including a coaxial torque shaft extending through said propeller shaft and said screw-jack for applying reversible driving torque to said differential gearing.

6. In combination with a variable pitch marine propeller having a hollow hub and a plurality of blades mounted axially rotatably thereon to vary their pitch, of mechanism operatively mounted within said hub for varying the blade pitch in unison comprising, a power screw-jack having a rotary driving screw extending rotatably within and coaxially of said hub mounted in bearings so as to be held against axial movement, and a translatable nut in the form of a cross-head mounted coaxially on said screw so as to be translated thereby and guided by said hub to slide axially without rotation, a sliding block linkage comprising a pin, a slot and a sliding block interposed therebetween operatively connecting said cross-head to said blades so as to turn said blades about their axes, and power means including differential gearing for applying reversible driving torque to said rotary screw.

'7. In combination with a variable pitch propeller including a hollow hub, of a plurality of blades mounted in said hub for axial rotation each about its longitudinal axis to vary their pitch, and of mechanism operatively mounted within said hub for rotating said blades axially in unison comprising, a power screw-jack mounted coaxially in said hub between said blades including a rotary jack-screw rotatably mounted in bearings in coaxial relation to said hub and a translatable combined nut-and-cross head mounted on said screw and guided by said hub for coaxial movement only, a mechanical movement for converting translatory motion of said nut into rotary motion of said blades about their axes comprising a slot, a pin, and a sliding block working between them, power means including differential gearing for rotating said screw, and thrust bearing means for supporting said screw against axial displacement.

8. A variable pitch marine propeller having, in combination, a hollow propeller shaft and a hollow hub mounted coaxially on one end thereof, and a plurality of blades mounted in radial sockets of said hub for rotation each about its own longitudinal axis; torque multiplying mechanism operatively mounted within said hub comprising a power screw-jack, including a hollow 10 rotary jack-screw extending rotatably within and co-axially of said hub, and differential gearing having a large torque gain ratio connected to drive said jack-screw; power means for applying torque to said differential gearing including a torque shaft passing coaxially through said propeller shaft and said jack-screw, and means operatively connecting said power jack to said blades for rotating said blades axially in unison.

9. In combination with a reversible pitch marine propeller including a tubular propeller shaft having a hollow hub mounted coaxially on one end thereof and a plurality of bladesmounted for axial rotation in said hub; of torque amplifying mechanism operatively mounted within said hub comprising planetary differential gearing coaxially disposed within said hub, a power screwjack including a hollow rotary jack-screw mounted coaxially within said hub so as to be driven by said gearing, a mechanical movement mounted within said hub for connecting said power screw-jack to said blades to rotate them axially in unison; a torque shaft extending rotatably and coaxially through'said jack-screw and operatively connected to drive said planetary differential gearing; and power means carried by said propeller shaft at the end opposite to the hub for applying reversible torque to said torque shaft.

10. In a controllable and reversible pitch marine propeller system including a tubular propeller shaft, a hollow hub, and axially rotatable blades carried by said hub, in combination, torque multiplying mechanism operatively mounted within said hub for rotating said blades axially in unison comprising planetary differential gearing mounted coaxially in said hub, and means including a screw-jack mounted between the inner ends of said blades operatively connecting said gearing to said blades so as to ro tate the latter axially; a torque shaft extending rotatably in and coaxially through said propeller shaft and into said hub and operatively connected to drive said planetary gearing; and an electrically energized power unit, including a reversible electric motor, carried by said propeller shaft at the end remote from said hub and operatively connected to drive said torque shaft.

11. A controllable and reversible pitch propeller system having, in combination, a drive shaft, a liquid-tight tubular propeller shaft, 9. liquid-tight hollow hub having radial sockets fixed tightly on one end of said propeller shaft, and blades having journals rotatably but tightly secured in said sockets; mechanism within said hub for rotating said blades in unison including a power screw-jack mounted between said journals, and torque multiplying planetary differential gearing mounted operatively within and coaxially of, said hub; a torque shaft extending coaxially through said propeller shaft and into said hub and operatively connected to drive said gearing, and a liquid-tight combination power unit and coupling drivingly connecting said drive shaft to said propeller shaft.

12. In a variable-pitch propeller system, the combination of a hollow hub, a plurality of blades carried thereby and so mounted as to be capable of angular adjustment each about its own longitudinal axis for varying the effective pitch of the propeller, and mechanism operatively mounted substantially within said hub for turning said blades axially in unison while operating under load comprising, planetary differential gearing mounted coaxially in the outer end of meson ll i h lb a P Q screw-jack operatively' mount edcentrally in said hub between the inner ends of said blades and including a rotary jaclg screw operatively connected to said gearing so as tobe blades inunison including a power hollow screwe jack including a jack-screw mounted rotatably and. coaxially in said hub, speed-reducer differential gearing mounted in said hub'in the end op.- posite said propeller shaft'and operatively connected to, drive said jack screw, and a torque transmission shaft passing coaxially through said jack-screw operatively connected for applying driving torque to Said speed reducer differential gearing.

14. In a controllable.v and reversiblepitch liquid propeller, thecombinat pn of a, hollow hub, blades carried thereby and so mounted as, to be capabl of angular adjustm n a a o its ownlo gi dinal axis. torque am lifying mechanism mounted operatively in'said hub fo an.- eu a y ad ust ng sai bladss aid mechan i lud n a power jack h t isv a Incl-10W ta y jack-s r w mou ted centrally with n, and caxially of, said hub and. differential earing mounted coaxially in said hub for driving said jaCkrSCreW, andpower means including a. t rq e ran i on haft pa in coaxially hrough said jack-screw operatively connected for driv ing, said difierentialigfialing,

15. In a variable pitch marine propeller, the combination of a tubular propeller shaft, a liq, uid t sh hub fiXBd tightly to, the out-board end thereo a pl rality of bla es arr ed y said hub and so mounted as to be capable of angular adjustment each bou ts own l ng tu inal, axis. ahollcw rotary DQWer screw rotatably held oen: trally d a ia l-y Within said. ub, a mb n d -an os head me ber mounted oaxially onsaid screw, guide means inside said hub holding said member against rotation with said screw but permitting axial movement thereon, means operatively connecting said member to said blades to turn each about its own axis by axial movement of said member on said screw; and means for rotating said power screw including differential gearing operatively mounted co axially in said hub, and a torque transmission shaft extending co-axially though said power screw operatively connected to drive said differential gearing.

HARRY J. NICHOLS.

REFERENCES CITED The following references are of, record in the f le of this patent:

UNITED STATES PATENTS Number Name Date 1,892,404 Messing Dec. 27, 1932 1,951,640 Allner Mar. 20, 1934 1,967,302 Gannett July 24, 1934 2,028,448 Harza Jan. 21, 1936 2,073,044 Andrews Mar. 9, 1937 2,124,078 Palmer et al. July 19, 1938 2,161,647 Whiskr une 6 1939 2,337,613 Martin Dec. 28-, 1943 2,344,029 in Mar. 14, 1944 2,3 0,15 H o e al- Fsb- 2 .9 2 392,364 Caldwell et al. Jan. 8, 1946 FOREIGN PATENTS Number Country Date 399,313 Great Britain Oct. 5, 1933 412,434 Great Britain, June 28, 1934 489,353 Great Britain Oct. 19, 1936 305,700 Germany June 15, 1917 344,283 Germany Nov. 5, 1 919 313,191 Italy Dec. 18, 1933 25 Italy ---=--.s-.- ul 8 1 119,550 Switzerland May 16, 1927 OTHER REFERENCES American Society of Naval Engineer-s Journal, vol. 521940 (Figs. 20 and 23; Controllable Pitch Propellers). 

